why the disease poses long-term health risks even after mild forms

“Living with the virus.” When it appeared, this slogan described a distant future. It now sums up the attitude held in most European countries, including France, where health restrictions have all but disappeared. More than 130,000 people are testing positive for Covid-19 every day, a total that would never be reached before the end of 2021, but the issue has faded from public debate. But the virus has not stopped being dangerous. It still kills an average of 101 people a day, most of them vulnerable or unvaccinated. A number of recent studies have also lifted the veil on the long-term effect: after infection, the risk of other pathologies increases, even those that are not a risk factor, do not develop a severe form and are not affected by the Covid long.

In April 2021, a first study by three researchers from the University of Saint-Louis (USA) was published by the journal Nature*, identified a variety of health conditions that were more common in people with Covid-19. Using an extensive health database of US Army veterans, the authors had compared nearly 5 million non-ill people and 77,000 people who tested positive, starting on day 30 after their infection. Five months later, they had more breathing problems and suffered more “Disorders of the nervous and neurocognitive systems, mental health, metabolism, cardiovascular system, gastrointestinal tract, malaise, fatigue, musculoskeletal pain and anemia” than people with a similar profile who have never tested positive. Even non-hospitalized patients showed this consequential risk.

Since then, this database has been used for several studies by the same team, including one on cardiovascular risk that was published in February Nature*. “It shows a risk multiplied by 1.5 or 2 in all events”, not just the well-known heart inflammation in Covid 19 patients, observes Ariel Cohen, former President of the French Society of Cardiology. In the case of those who tested positive (more than 150,000 were observed), the risk of a stroke in the year after infection multiplied by a factor of 1.52, the risk of pulmonary embolism by a factor of 2.93, and that of acute coronary syndrome by a factor of 1.72 .

“At the beginning of the pandemic, we thought that Covid-19 was simply a source of decompensation for existing risks”, recalls Ariel Cohen. That is, people who are predisposed to these problems have declared them on the occasion of an infection with Sars-CoV-2. The results of these American researchers are “A surprise”he admits.

“This study shows that there is an increased risk associated with the infection itself and that it does not go away over time as we thought.”

Ariel Cohen, former President of the French Society of Cardiology

on franceinfo.fr

While it is not entirely clear how the virus causes such consequences, observation of patients has already shown “that the virus attacks the wall of the blood vessels”which in particular favors the occurrence of blood clots, explains Olivier Robineau, specialist in infectious diseases at the hospital in Tourcoing (Nord).

Patients cured of Covid-19 are also at higher risk of developing kidney-related pathologies, according to a study by the same American team, published in November Journal of the American Society of Nephrology*. In particular, the data indicate a three-fold risk of end-stage renal disease in ex-COVID-19 patients (and 2.15-fold in non-hospitalized patients). Because the virus causes vascular problems, it can actually affect a large number of organs. “All of these organs are vascularized. As soon as the function of the artery is changed, there is a risk that they will be affected.”explains cardiologist Ariel Cohen.

In the minds of the general public, Covid-19 is more associated with symptoms such as loss of taste and smell. But they point out that the virus also affects the brain and nervous system. In particular, long Covid patients report difficulty concentrating and a form of “mental fog”. A study of the brains of monkeys infected with the virus, published Jan nature communication*showed damage “can lead [à ces] long-term neurological symptoms of long covid”also in animals that have not developed a severe form.

“Researchers warn of dementia risk” favored by the damage caused by the virus, reports Olivier Robineau. The authors of an article published by the journal Science* In January, note that the damage is observed in some patients “raise the possibility that the infection could accelerate or trigger the future development of neurodegenerative diseases such as Alzheimer’s or Parkinson’s.”

This hypothesis remains more vague at the moment than that of cardiovascular problems, nuance Olivier Robineau, who recalls that these disorders would take years to appear. However, health data from American veterans includes an increased risk of cognitive decline (multiplied by 1.8) or depression (multiplied by 1.39) in the year after infection, according to a study published Feb. 16 British Medical Journal*.

This statistical approach has limitations. A recent study of this data, published March 21 in The lancet*, noting that people cured of Covid-19 are more likely (+40%) to develop type 2 diabetes in the following year. The pandemic will go “A Legacy of Chronic Disease”says its lead author, Ziyad Al-Aly, in Nature*. Eric Renard, vice president of the Francophone Diabetes Society, sees no evidence that the virus itself causes diabetes.

“The most obvious connection is a revelation connection. Covid-19 puts a strain on the body, which can reveal latent diabetes.”

Eric Renard, Vice President of the Francophone Diabetes Society

on franceinfo.fr

The possibility that the virus is only a trigger is recognized by American scientists and is in line with what is observed after other infections. Eric Renard does not believe in the risk of an epidemic of type 2 diabetes: “These patients will just have discovered their diabetes in an unusual way, with insulin treatment right away, but they will comply.” The study has the merit of drawing doctors’ attention to the interest of measuring blood sugar levels in people who have recovered from Covid-19, particularly if they have other risk factors for diabetes.

“You have to keep calm”, argues infectious disease specialist Olivier Robineau. Recent studies show “an undeniable over-risk” certain pathologies for Covid-19 patients, “but to events that remain rare. We will not have an epidemic of pulmonary embolism.” He also recalls that other elements, such as tobacco and diet, are risk factors that are much more important in the development of cardiovascular diseases, for example.

“There is no reason to panic for people who have cleared the infection and are perfectly fine”adds Jérôme Larché, officer for surveillance of the long Covid in Occitania. “We just have to encourage them to consult if there’s a problem.” Before all people cured of Covid-19 are monitored, it is already necessary to identify and guide those who face persistent symptoms, a “big challenge”, he explains. Another priority “is intended to compensate for the delayed care of many patients due to the pandemic”remembers cardiologist Ariel Cohen.

Research into the consequences of Covid-19 is still in its infancy. Other work needs to confirm them and refine the measurement of the risks posed by Covid-19, among populations more representative than US Army veterans, an older-than-average public, and a male-dominated public.

Moreover, according to the same studies, these risks of Covid-19 remain proportional to the severity of the disease: a reassuring observation, while the rise of the Omicron variant and vaccination have reduced the proportion of severely affected patients. But for Jérôme Larché, what we know about the aftermath is encouraging “activate all possible levers to avoid contagion, from the vaccine to wearing a mask”. “Covid-19 is anything but a small, temporary infection without consequences”he remembers.

* Links with an asterisk lead to publications in English.

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